FotoBento PhotoPro
Everyday Photography Tools
My Blue Heaven - Divine White Balance
Problem: Sometimes everything in your photo looks yellow, or with flash it all turns blue. This difference between what you see and the resulting image is the color cast.
Fotobento Solution: Make sure your camera “sees” what you see by adjusting the white balance on your camera. Even though it’s called White Balance, adjusting it will improve all colors.
Two variables affect the white balance of the image recorded on your camera:
1. The color composition of the scene being photographed.
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2.The light source illuminating the scene.
What is White Balance? Adjusting your white balance removes the color cast on your photo by matching the white point your camera uses in recording the scene to the temperature (or white point) of your light source.
What is White Point? When you take a photo, your camera’s digital imaging sensors only record how much red, blue or green light is reflected off your subject.
To re-create the image from the raw data, the camera selects a point to represent the color white. The color temperature of this pixel is then compared to the color temperature defined (by you manually or as measured by the camera) as white for your light source. The rest of the colors in the image are then calibrated based on this white point.
In other words, the processor, in your camera or computer, adjusts the amount of red, blue or green to compensate primarily for the red or blue tendency of the light source (more on that below). So this one white point has a disproportionately large impact on the color of the resulting photo.
The white point matches a pixel to a temperature: Relative to the source of the light, the white point is the temperature at which the white portions of the image look white. Balancing the white point of the composition with the temperature of the light can be assigned automatically in most cameras. It can also be set to more closely approximate actual conditions.
For example, a white piece of paper will look different depending upon the type of light shining on it. Indoors, under an incandescent bulb, the camera will record the
white paper as slightly reddish/yellow. Turn on the flash, and the paper will look slightly bluer.
3/31/09
Comments Widget
What is color temperature? The color of a light source is measured in degrees Kelvin (K) and is referred to as its temperature. Daylight’s color temperature is roughly 5000-5500K. A light source with a color temperature close to 5000-5500K will appear white because it is an approximately equal mix of red, blue and green light.
A light source with a low temperature, below 5000K, will give off light in the reddish end of the light spectrum. In other words, a slightly red color cast. The effect of this light will be to “warm” the color of the photo. This is particularly flattering in portrait photography. Warm refers to the light source’s effect on the person or object in the picture, whereas the temperature measures the output of the light source.
Light sources with a higher temperature than 5000K will tint the photo bluish. These high temperature light sources are often said to be “cool” light because their effect is to cool down the look of the resulting photo.
Why don’t we see this? Within a broad range, our eyes adjust to the quality of the light so that the white piece of paper looks pretty much the same in most lighting situations.
The Strands, Dana Point, CA
This nifty chart shows the estimated temperature values of different light sources and their effect (color cast) on daylight film. The chart shows the color cast that will occur. Click on this chart to go to the original link. Then roll over the colors on the chart and see what the photo would look like with proper color correction. I don’t own any Canon equipment but this chart alone would make me take a second look the next time I’m in the market.
Estimated temperature values of different light sources
Bright Light Source = High temperature light = bluer photo = cooler light
Dark Light Source = Lower temperature light= redder photo= warmer light
Recap:
Light temperature (measured in degrees Kelvin) measures the cause – the light source.
Light quality (described as warm or cool) describes the effect - the warming or cooling change light makes on the perceived color of an object.
Next Time: Situations when Auto White Balance doesn’t get it right, examples and links.
